Numerical study of wave run-up on a fixed and vertical surface-piercing cylinder subjected to regular, non-breaking waves using OpenFOAM

Abstract

In wave-structure interaction, wave run-up is an important phenomenon that needs to be considered in the design of offshore structures. A thorough understanding of the physics of the nonlinear flow phenomena is necessary for the better insight into the run-up phenomenon. The present work, primarily, is focused on the hydrodynamic simulation of wave run-up and mainly seeks to evaluate the importance of wave scattering types identified by Swanet al. (2005) and lateral progressive edge waves on nonlinear wave amplification around a single fixed cylinder. The analysis is performed numerically using Navier-Stokes solver based on OpenFOAM over a range of wave steepnesses and wavelengths. In order to study wave-cylinder interaction, a numerical wave tank is utilized which includes IHFOAM toolbox for wave generation. For the simulations, the cylinder is assumed vertical and surface piercing with a circular cross-section and the incident wave is considered fifth-order Stokes, regular and non-breaking in deep water. The obtained numerical results that are mainly analyzed in this study include local surface elevation, the scattered wave field around the cylinder and the wave forces. A grid-space and time step refinement study are carried out to evaluate the performance and accuracy of numerical wave tank. The numerical results are compared with experimental data provided by ITTC (OEC), (2013) and a good agreement was obtained which indicates that OpenFOAM is very capable of accurate modeling of nonlinear wave interaction with offshore structures. The harmonic analysis for both short and long wave cases indicates that the scattered wave field around the cylinder involves high harmonics wave run-up. It is confirmed that even the wave-structure interaction caused by the linear incident wave, can lead to weakly nonlinear wave amplification around the cylinder. In the case of long waves cases, the harmonic loading involves at-least third harmonics due to the occurrence of the second wave run-up at the front part of the cylinder.